Unusual ticking noise in 4stroke 1 cylinder engine! VIDEO INCLUDED!

Unusual ticking noise in 4stroke 1 cylinder engine! VIDEO INCLUDED!

Hi, I`m completely lost. I`m studying mechanics but this is just out of my league. So this is Honda Cbr 125 RW7 - Fuel injected version. I Have replaced piston rings, head gasket, and cam chain tensioner adjuster to a manual one. Havent touched or adjusted the valves tho. The sound arrived just in 1 day- straight away. So i took rocker cover off to inspect it. So. What happens is - when the INLET valve is CLOSING, just before it closes it makes a TICK. Doesnt matter how fast the engine runs, the tick noise even appeared when i was turning the engine really slowly. When the engine is at idle - I have few descriptions for that sound - sounds like diesel - or sewing machine. Also - rocker arm doesnt seem loose and the tick only happens when the inlet valve closes. ( didint notice power lose.)
Anyway, any help will be appreciated, thank you so much for reading,
Arturas.

P.S. I`m quite new to these forums so I am not sure if i am allowed to post a thread seeking for some advice. Sorry for any problems caused.

I thought maybe I would see the valve sticking a little on its way closed, as if the stem is bent, but I couldn't see evidence of that on the video.
I did distinctly hear the click, but I can't localize it from here.

Suggestions:
Manually crank it to near firing position, and see if you can open the valve with a lever, acting directly on the spring retainer if possible. You may not be able to stroke it all the way open, but there should be a little piston clearance left even at TDC. Then try it with the piston at BDC. I'd think you'd be able to feel any binding in the stem, but I'm not convinced that that's what's causing the noise.

Try some more slow hand cranking, and see if you can correlate the click with something else.

Possibly the valve slamming shut due to a very wide valve clearance. Having an excessively wide clearance means the cam's closing ramps don't come into play and the valve drops the last little bit onto its seat.

Coils possibly clicking over each other because very small deformation or damage in the spring seat area has pulled the two valve springs out of concentric alignment.

Quote (BigClive)

Possibly the valve slamming shut due to a very wide valve clearance. Having an excessively wide clearance means the cam's closing ramps don't come into play and the valve drops the last little bit onto its seat.

Can't be this- the noise happens consistently in the middle of the valve's travel, while the lifter is still under full spring pressure.

If it is, I think jgKRI could be on to something. Good eye on the nested springs jg. Charge that cylinder with air to hold the valve up, and remove the springs and look for a rub on the springs. Inside of one of the outer spring and outside of the inner. Could be something as simple as some contaminant sitting under the end of the spring forcing it off center.

And how could you do that work you said you did, with out any attempt to adjust valve lash? Do that first and then see if it still makes the noise.
Also have you made an attempt to listen what area the noise is coming from? Do you hear it near the valve? Or more in the case?

I recently had a 4 stroke outboard motor showing a similar symptom, the problem was a corroded inlet valve stem.
The lifter would push the valve down for the inlet stroke, The piston would descend and the lifter would lift to allow the valve to close.
The valve would stick just short of closing, as the piston velocity increased the gas flow would shut the valve with an audible click.
Could you have a similar problem?
B.E.

So! Im surprised that there are many friendly and ready to help people! Thank you all so much for advice!
- Ive set valve cleaeance to manufacturers specs, still the same thing.
- I did suspect the springs that are worn, it could be it!
- This bike has no service history, and i already did 13k miles without ANY valve adjustment. I take it will be something loose or broken.

Anyway! I took 2 days off from work, and I'm going to take the cyl head off and fully inspect every sigle bit! I will keep you guys updated, and again, thank you so much for help, I do really appreciate it!
Best regards, Arturas

So! What i have found out tonight :
Took the cylinder head off. Checked for excessive freeplay on rocker arms - they are in great shape. Camshaft doesnt seem damaged so as its bearings.
-Turned the engine over quite a few times while holding timint chain on my finger - ive heard no sound and it was really smooth. So I assume bottom end is fine.
- Then i started dismantling valves. The inlet one- the one that was making the weird sound, its collets FLIED AND I MEAN JUMPED OUT like crazy!! I think that was the sound! Probably springs got weak and collets went out of position.
-I have ordered new valves, stem seals, a gasket and new set of springs for new valves. I will see how it will go but im quite sure it will be a fix.

I would be inclined to put that valve back together and see what happens. My suspicion based on your last post is that one of the keepers was out of position. I can't see a spring suddenly going lame, unless something happened to the motor prior to the head & piston work.

You could also add a load to the spring from one of the valves not having issue and confirm that you get the same displacement. This would rule out a suddenly lame spring.

Sounds like you've narrowed down the problem. Just thought I'd toss this in...

I noticed a virtually identical noise on a 650 Triumph twin, while setting the timing - just before the valve began to open, and just before it started to close, it would make a noise like that. The motor turned out to be in terrible shape otherwise, so I tore it down.

What I found blew my mind... the cam lobe on that valve was loose on the shaft! It had cracked where the lobe joined the shaft, all the way thru the lobe. That allowed the lobe to rotate on the shaft a very small amount, making that noise when spring pressure was applied on the opposite side of the lobe. Never seen or heard of such a thing before or since.

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